I've just looked at the record of my maternal gran and my parents again to see who the redacted person was and it has been opened - yippee. It is one of my mother's nieces (so one of my cousins). She was born in 1931 and is shown as "at school", she was 8 then and I would guess was just visiting. Interestingly, although she didn't marry until 1955 (some 14 years later), her maiden name has been crossed out and her married name inserted. She died in 2002.
There are also some redacted names living with my paternal gran but they've not been opened yet. I think one is probably one of her daughters born 1917 who only died 2011 and her youngest son born 1913 died 1975. My dad born 1912 is shown living with my mum, and his twin sister is shown with her mum, so I'm guessing the redacted people are younger than born 1912. If not, then I have no idea who these people are. I'll just keep checking until the records are opened.